Hissing brake pedal?

[Darrman]

I have noticed that the brake pedal is a little soft, been like that since I got it. I check the fluid reguarly, never any difference, it has new pads front and back, rotors and drums. However I noticed the other day that when its quiet in the car and you are holding the brake, you can hear a hissing noise from under the dash. I have reciepts from the previous owner and a mechanics recomendation of a new booster, but this is from about three year ago.
I am a little dumb when it comes to brakes, and since I really need them, I want them to work perfect, (even tho these '91's are horrible braking systems). Can anybody confirm any of this?

 

[TarHeel085]

sounds like the booster itself is leaking or you have a vacuum leak at the booster. if the booster was never replaced and it was recomended three years ago, then thats your culprit.

 

[Darrman]

Hmmm, sounds like I will have something to work on during Christmas off week. I cant think of anything else it could be, so I guess I will look into it. Is there some way of determining for a fact if its leaking or not, or where? Thx for your help.

 

[TarHeel085]

get under the dash and put your hand where the plunger goes into the booster and press the pedal, if the hissing is really loud under there then thats it, and check for air comming out of it. this is of course with the motor running. but you might not be able to feel it, it may be leaking internally, but either way, it almost has to be the booster, especially since your pedal is soft.

 

[1IronMike]

TarHeel085, the air would not be comming out, but going in from inside the cabin. Remember that the Vaccuum is applied in the engine bay.
Most likly a small hole in the diaphram caused by rust and wear. Easy swap out should fix you right up.

 

[86caprirs]

Needs a brake booster.